Variable compressibility roller

Abstract

The present invention relates to a variable compressibility layer in rollers or flat pulleys. The present invention provides a smooth-surface roller that will "spread" a web being conveyed by a roller, or urge flattening and prevention of wrinkles in the web. It will also assist in the centering of the web being conveyed on web-handling equipment. If a roller is small, it may be used as a flat pulley, wherein the present invention causes a belt to track in the center of the pulley.

What is claimed is: 
     
       1. A web conveying article comprising: a first layer, having an inner and an outer surface, with the outer surface being substantially smooth so that the article has a substantially constant outer diameter;   a second layer, having an outer and an inner surface, the outer surface being an inverse of the inner surface of the first layer, with one of the layers being a compressible layer of a thermoplastic or elastomeric material which contains voids therein, which layer is thicker at the ends of the web conveying article than in the center; and   a rotatable support, wherein each of the layers is in concentric relation about the rotatable support.   
     
     
       2. The article of claim 1, further comprising a base layer, concentrically arranged about the rotatable support, and having an outer surface for supporting the first and second layers. 
     
     
       3. The article of claim 1 or 2 wherein the material of the compressible layer is selected from the group consisting of a polyurethane, a thermoplastic polymer, or an elastomer. 
     
     
       4. The article of claim 1 or 2 wherein the compressible layer has a concave shape in cross-section. 
     
     
       5. The article of claim 1 or 2 wherein the compressible layer has at least one step between relatively thicker and relatively thinner regions. 
     
     
       6. The article of claim 1 or 2 wherein the thickness of the center portion of the compressible layer is zero. 
     
     
       7. The article of claim 1 or 2 wherein the compressible layer has a thickness which constantly decreases inwardly toward the center portion of the article to a minimal or zero thickness. 
     
     
       8. The article of claim 1 or 2 wherein the compressible layer has a wide U-shaped cross-section, wherein substantially all of the center portion of the foam has essentially the same minimal thickness. 
     
     
       9. The article in claim 1 or 2 wherein the compressible layer has at least one relatively thicker and one relatively thinner region, wherein each region progressively inward toward the center portion of the article is connected by a constantly decreasing thickness of the compressible layer. 
     
     
       10. The article of claim 1 or 2 in the form of a roller. 
     
     
       11. The article of claim 1 or 2 in the form of a flat pulley. 
     
     
       12. A method of manufacturing a web conveying article comprising the steps of: providing a rotatable support;   providing a first layer concentrically about the rotatable support; and   providing a second layer concentrically about the first layer to form a web conveying article having a substantially smooth outer surface so that the article has a substantially constant outer diameter, wherein one of the first and second layers is a compressible layer of a thermoplastic or elastomeric material which contains voids therein, which layer is shaped with a greater thickness near its ends and with a reduced thickness in its central portion.   
     
     
       13. The method of claim 12, further comprising adding a base layer, which is concentrically arranged about the rotatable support, before providing the first and second layers. 
     
     
       14. The method of claim 12 or 13 wherein the material of the compressible layer is selected from the group consisting of a polyurethane, a thermoplastic polymer, or an elastomer. 
     
     
       15. The method of claim 12 or 13 which further comprises providing the compressible layer with a concave curved shape in cross-section. 
     
     
       16. The method of claim 12 or 13 which further comprises providing the compressible layer with at least one step between relatively thicker and relatively thinner regions. 
     
     
       17. The method of claim 12 or 13 which further comprises reducing the thickness of at least part of the center portion of the compressible material to zero. 
     
     
       18. The method of claim 12 or 13 which further comprises providing for the thickness of the compressible layer to constantly decrease inwardly toward the center portion of the article to a minimal or zero thickness. 
     
     
       19. The method of claim 12 or 13 which further comprises providing the compressible layer with a wide U-shaped cross-section, wherein substantially all the center portion of the compressible layer is of essentially the same minimal thickness. 
     
     
       20. The method of claim 12 or 13 which further comprises providing the compressible layer with at least one relatively thicker and one relatively thinner region, wherein each region progressively inward toward the central portion of the article is connected by a constantly decreasing thickness of the compressible layer.